Human Kidney Cathepsins B and H Activate and Lower the Molecular Weight of Human Inactive Renin

Cathepsins B, H, and D, extracted from human kidneys, activate human inactive renin. Inactive renin, obtained from human kidneys, contains two components of Mr 53,000 and 50,000. Upon incubation with 0.5 μM cathepsin B, the Mr of the larger component decreased progressively to 45,000 (similar to the Mr of active renin) without appreciable loss of renin activity. Cathepsin H also activated and decreased the Mr of kidney inactive renin. Plasma inactive renin was activated by the thiol proteases, cathepsins B and H, with less reduction in Mr than that observed in kidney renin.